The function of various network protocols causing the problems of setting up a subscriber-mobile station connection will be further illustrated with reference to FIG. 2, which shows a more detailed internal structure of FN, PLMN-A and PLMN-B.
Let's first consider the case A mentioned above, where a fixed subscriber wishes to set-up a call to a mobile station of PLMN-A. Here the fixed subscribers SS1-SS4 are respectively connected to a private branch exchange PABX 1, 2 (a customer premises equipment CPE) via an internal access protocol 1. The private branch exchanges PABX1, PABX2 are linked via a access protocol 2: DSSI or a national access protocol to a ISDN/digital originating exchange O-EX1. This originating exchange O-EX1 is connected to the ISDN/digital terminating exchange T-EX via a ISDN user part (ISUP) protocol 3, a national user part (NUP) protocol or an analog signalling protocol. The network interface NI uses a ISUP, a national user part (NUP) protocol or analog signalling protocol 4 for a connection to the PLMN-A network. The just mentioned protocols are used for communication between the different entities in the communication network. The signalling system No.7 is used to transport these protocols.
As aforementioned, the ISDN user part (ISUP), a mobile application part (MAP) or a national user part (NUP) are used as network protocols. The combination of different protocol interfaces required to signal an ISDN (or digital) originating call to a PLMN-A may however filter out required compatibility information involved in a basic service mobile termination call MTC, as explained above.
In the above mentioned case B, where a mobile station MS* in the PLMN-A wants to communicate with another mobile station MS1-MS4 in the PLMN-A, respective set-up messages are send also to an originating exchange O-EX2 of FN and again the various protocols used may filter out compatibility information. Likewise, in the above mentioned case C, where a mobile station MS* in the PLMN-B wants to communicate with another mobile station MS1-MS4 in the PLMN-A, respective set-up messages are send also to an originating exchange O-EX3 of FN and the various protocols used may filter out the respective compatibility information (It may be noted that the schematically illustrated HLR in PLMN-B is only used for terminating a call to a mobile subscriber in PLMN-B, however, it is not involved for setting up a call from a mobile subscriber of PLMN-B to a mobile subscriber of PLMN-A)
Hereinafter it will be explained how the setting up of different types of calls is conventionally done. First, case A will be illustrated. In order to still allow the setting-up of different types of calls between the fixed subscriber stations and the mobile stations, the conventional technique is to use a method called "multiple-numbering scheme", in order to determine the required bearer capability in the mobile radio communication network (reference 2!). Since this technique uses devices of the PLMN network, e.g. a home location register HLR and a visitor location register VLR, these fundamental devices of every mobile radio communication network are briefly described with reference to FIG. 2. As is well known, the mobile radio communication network is divided into different cells 0, 1, 2, 3, which each have at least one base station transmitter BTS controlled by a base station controller BSC. There are several mobile services switching centers MSC, wherein the first MSC, to which a mobile terminating call is routed from the FN, is called the gateway mobile services switching center GMSC, as is shown in cell 3 in FIG. 2. The GMSC interrogates a home location register HLR, which is a database used by the PLMN to manage all mobile subscribers (see FIG. 3b), and performs the routing function to the mobile switching center MSC, where the mobile station is located (e.g. in cell 0). The mobile services switching center MSC performs all the switching functions needed for mobiles located in an associated geographical area (cell). Interworking with other networks needs the presence of specific functions associated with the MSC. These functions are contained in the interworking function (IWF).
A visitor location register VLR is a database used by the PLMN to dynamically store information of the mobile subscriber, such as the location area, where the subscriber is located or is roaming. The VLR also contains devices to handle mobile originating and terminating calls. Such an interconnection of HLR, VLR, MSC and a base station system is also disclosed in DE 44 15 734 C1.
Since the "multiple-numbering scheme" is essentially provided to derive a bearer capability BC necessary for the type of call made by the fixed subscriber, hereinafter the role and requirements for bearer capabilities in PLMNs will be further highlighted.
The bearer capability BC is required to define a bearer service or teleservice, i.e. it defines the technical features of the call as they appear to the user at the appropriate access point, i.e. the modem etc. This bearer capability can optionally be complemented by the higher layer compatibility information and the lower layer compatibility information (the purpose of the higher layer compatibility information is to provide a means to use by some remote ISDN-user for compatibility checking). It is used for teleservices characterization with the lower layer attributes included in the bearer capability. The lower layer compatibility LLC information element is to provide a means to use for compatibility checking by an addressed entity; e.g. a remote user, an interworking unit, or a network node higher layer function addressed by the calling user. The lower layer compatibility information element is transferred transparently between the call originating station, i.e. the calling mobile subscriber, and the address station (reference 5!: Integrated Services Digital Network (ISDN); User-Network Interface Layer 3; Specifications for Basic Call Control; ETSI, European Telecommunications Standards Institute; December 1990). That is, the bearer capability represents the type or characteristic of a mobile call.
The call originating subscriber SS1-SS4 initiates the call from a subscriber station linked to the public switched telephone network PSTN (see FIG. 2) or an integrated services digital network (ISDN) or even from another PLMN. In this respect, the called party is of course the mobile station in the PLMN-A, as is illustrated in FIG. 2. For example, in setting-up a call having a non-speech type, if interworking between the PLMN and the PSTN is required, the "multiple-numbering scheme" technique is used to provide a mobile bearer capability BC to the called mobile station with ISDN number MS-ISDN (the MS-ISDN is the mobile subscriber ISDN identity assigned to a calling subscriber for mobile originating calls or called subscriber for mobile terminating calls).
When setting up a call from a fixed subscriber station to a mobile station, this MS-ISDN is for example the calling number of the mobile station. In GSM- or DCS- or PCS-networks, an MS-ISDN addresses a mobile subscriber as opposed to a specific location or apparatus used by the mobile subscriber. Thus, the MS-ISDN addresses directly the mobile subscriber independent from the particular mobile station into which the mobile subscriber has inserted his SIM-card. That is, the "multiple-numbering scheme" provides the requested information about which mobile bearer capability BC to use together with the MS-ISDN during a call-set up request. An ISDN-interworking requires the signalling of such bearer capability information (i.e. bearer capability, lower layer and higher layer compatibility), to derive a proper call during call set-up. This information is conveyed to the customer premises equipment (e.g. the private branch exchange PABX or an ISDN-terminal), to further define the specific requirements of the type of call.
Independent of the type of fixed network (ISDN or PSTN), the first stage in setting-up a call is to exchange some signalling information between the calling subscriber station and the mobile radio communication network, in order to establish a signalling path between them.
The second stage is the derivation of the appropriate bearer capability for the type of call originated by the subscriber station of the fixed network or another mobile station. Here, ISDN and PSTN are different. In the ISDN-PLMN-A case, the second stage at call-set-up is the transfer of some compatibility information by the ISDN-protocol to the PLMN in order to characterize the requested basic service (bearer service or teleservice). In case this complete compatibility information is indeed received by the PLMN-A, it will provide the bearer service, which is adapted to handle the basic service which is characterized by the compatibility information transmitted.
However, as afore-said, the use of several network protocols almost always destroys part of the compatibility information, which is subsequently not received in full at the PLMN-A, which is therefore at a loss which kind of bearer capability it should provide for the requested type of call.
The second stage for the PSTN-PLMN-A case also requires the provision of bearer capabilities. However, due to the analog speech nature of the PSTN, it was never adapted to provide some compatibility information, even if the type of call, which is originated, is a different call, e.g. involving the transmission of facsimile data instead of speech. For example, the fixed subscriber station may just hook up a modem and will indeed be able to transmit facsimile data, however, it cannot indicate to the PLMN-A, which kind of bearer capability is necessary in the PLMN-A, since the subscriber station itself has not transferred compatibility information which could characterize a requested bearer service. Thus, the PLMN (geared to an ISDN-interconnection) views a PSTN as a network providing a bearer service similar to an ISDN 3.1 KHz bearer service (since the PSTN in general provides an analog network with only 3.1 KHz voice or voice band data services). Hence, while the ISDN, PSTN interconnection to a PLMN-A is different in as much that the former does intend to characterize the type of call via some compatibility information (which however unfortunately does not arrive in full at the PLMN), and that the latter cannot provide any compatibility information at all even when requesting a non-speech type call, both are similar in the disadvantage, that the PLMN-A does not exactly know which kind of bearer capability it is supposed to provide for the type of call (type of bearer service or telecommunication service). To remedy this, conventionally the afore-mentioned "multiple-numbering scheme" is employed in the HLR, as will be explained in the following with reference to FIG. 3.
Even in the aforementioned cases B, C of communication of a mobile station MS* of PLMN-A or PLMN-B, respectively, and a mobile station MS1-MS4 of PLMN-A the same disadvantages of filtering compatibility information during call-setup occur, since the respective MSC* sets up the call through the FN by creating set-up messages to the respective O-EX2, O-EX3, which have the same format as those created by PABX1, PABX2. Again these messages undergo the filtering in network protocols 3, 4.
Multiple-numbering scheme
FIG. 3a, 3b show the signalling between the PLMN and the ISDN or PSTN. As may be seen from FIG. 3b, the main device responsible for handling the multiple numbering scheme is a specific arrangement of a home location register HLR. In the following, the PSTN-case and the ISDN-case will be treated simultaneously for simplification. Although only schematically illustrated in FIG. 3a, it should be understood, that the following procedure of setting up a call between a fixed subscriber and a mobile station of PLMN-A is similarly applicable to the case where the call set-up request comes from the mobile station MS* in PLMN-A or PLMN-B for communication with one of the mobile stations MS1-MS4 of PLMN-A.
As is seen in FIG. 3a, b, c, during the second stage of call set-up, the terminating exchange T-EX (independent of whether the call is originated from a fixed subscriber SS1-SS4 or a mobile station MS*) transfers via the network interface NI an initial address message IAM to the GMSC. This message has the following format for ISDN and PSTN:
PSTN: IAM (MS-ISDN.sub.k); PA1 a) The fixed subscriber or the mobile station MS* must employ a large number of MS-ISDN numbers for each and every different type of call or type of service (basic service or telecommunication service); PA1 b) the call set-up will fail, if a MS-ISDN is specified, which does not correspond to the specific type of call desired; PA1 c) the transmitting of compatibility information (in the ISDN-case B in FIG. 3c) only makes sense, if it arrives unfiltered, since only then the bearer capability can be derived directly without the multiple-numbering scheme. If the compatibility information arrives complete without being filtered by the network protocols, only then the HLR can make use of this transferred compatibility information for deriving the appropriate bearer capability BC. However, if the compatibility information is indeed filtered via the network protocols, then the HLR cannot use this information at all and compatibility information h as been transmitted in vain. PA1 to provide a communication system, a switching means and a method for setting-up call s of various types between a call originating subscriber and mobile subscriber of a mobile radio communication system, that are easy to use, require less storage space in the HLR and only require a single-number MS-ISDN for setting up a variety of different types of calls to the mobile subscriber. PA1 a) sending (S1, S2) a call set-up request (IAM, SRI) having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested from the subscriber to a switching means (PABX, CPE, O-EX, T-EX) of the fixed network; and PA1 b) transferring (S3, S4, S5) said call set-up request (IAM, SRI) from said fixed network switching means to a switching means (GMSC, HLR, VMSC/VLR, MSC) of the mobile radio communication network via a network interface (NI, ISUP); and PA1 c) comparing a content of said second portion of said call set-up request (SRI) having been transferred to the mobile radio communication network switching means with a number of bearer capability contours (BCC11-BCCN1; BBC12-BCCN2) predefined for each subscriber of the mobile radio communication network and respectively representing a specific service supported by the mobile radio communication network for handling the different types of calls; and PA1 d) selecting a predefined bearer capability contour which provides a best match to said content of said second portion; and PA1 e) composing a final mobile bearer capability (BC.sub.F) from said content of said transferred second portion and said best match selected predefined bearer capability contour; and PA1 f) allocating bearer capabilities (BC) in the mobile radio communication network in accordance with said final mobile bearer capability (BC.sub.F); and PA1 g) setting-up said call requested by said call set-up request to said mobile subscriber (MS) using said calling number of the mobile subscriber (MS-ISDN) and said allocated bearer capabilities. PA1 a) sending (S1, S2) a call set-up request (IAM, SRI) having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested from the subscriber to a switching means (PABX, CPE, O-EX, T-EX) of the fixed network; and PA1 b) transferring (S3, S4, S5) said call set-up request (IAM, SRI) from said fixed network switching means to a switching means (GMSC, HLR, VMSC/VLR, MSC) of the mobile radio communication network via a network interface (NI, ISUP); and PA1 c) comparing a content of said second portion of said call set-up request (SRI) having been transferred to the mobile radio communication network switching means with a number of bearer capability contours (BCC11-BCCN1; BBC12-BCCN2) predefined for each subscriber of the mobile radio communication network and respectively representing a specific service supported by the mobile radio communication network for handling the different types of calls; and PA1 d) selecting a predefined bearer capability con tour which provides a best match to said content of said second portion; and PA1 e) composing a final mobile bearer capability (BC.sub.F) from said content of said transferred second portion and said best match selected predefined bearer capability contour; and PA1 f) allocating bearer capabilities (BC) in the mobile radio communication network in accordance with said final mobile bearer capability (BC.sub.F); and PA1 g) setting-up said call requested by said call set-up request to said mobile subscriber (MS) using said calling number of the mobile subscriber (MS-ISDN) and said allocated bearer capabilities, PA1 Furthermore, this object is solved by a switching means (MNSW-A; GMSC, HLR, VMSC/VLR, MSC) of a mobile radio communication network (PSTN-A) having connected thereto a fixed network (FN, PSTN, ISDN, PSPDN) via a network interface (NI, ISUP) for setting-up calls of different types between a call originating subscriber (SS1-SS4; MS1-MS8) and a mobile station (MS) of the mobile radio communication network, comprising: PA1 a) a reception means (GMSC, HLR) for receiving a call set-up request (IAM, SRI) having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested from said subscriber transmitted from a switching means (PABX, CPE, O-EX, T-EX) of the fixed network; and PA1 b) a contour storage means (CM) for storing for each subscriber (MS1-MS4) of the mobile radio communication network a number of predefined bearer capability contours (BCC1, BCC2, BCCN) indicating services supported by the mobile radio communication network for handling said different type of calls; and PA1 c) a contour selection means (CSM) for comparing a content of said second portion of said received call set-up request (SRI) with said predefined bearer capability contours and for selecting a predefined bearer capability contour which provides a best match to said content of said second portion; and PA1 d) an assembly means (AM) for composing a final mobile bearer capability (BC.sub.F) from said contents of said received second portion (BC2) and said best match selected predefined bearer capability contour; and PA1 e) a setting-up means (HLR, VMSC/VLR, MSC) for allocating bearer capabilities (BC) in the mobile radio communication network in accordance with said final mobile bearer capability (BC.sub.F) and for setting-up said requested call to the mobile subscriber (MS) using said calling number (MS-ISDN) and said allocated bearer capabilities (BCi). PA1 a) a reception means (GMSC, HLR) for receiving a call set-up request (IAM, SRI) having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested from said subscriber transmitted from a switching means (PABX, CPE, O-EX, TEX) of the fixed network; and PA1 b) a contour storage means (CM) for storing for each subscriber (MS1-MS4) of the mobile radio communication network a number of predefined bearer capability contours (BCC1, BCC2, BCCN) indicating services supported by the mobile radio communication network for handling said different type of calls; and PA1 c) a contour selection means (CSM) for comparing a content of said second portion of said received call set-up request (SRI) with said predefined bearer capability contours and for selecting a predefined bearer capability contour which provides a best match to said content of said second portion; and PA1 d) an assembly means (AM) for composing a final mobile bearer capability (BC.sub.F) from said contents of said received second portion (BC2) and said best match selected predefined bearer capability contour; and PA1 e) a setting-up means (HLR, VMSC/VLR, MSC) for allocating bearer capabilities (BC) in the mobile radio communication network in accordance with said final mobile bearer capability (BC.sub.F) and for setting-up said requested call to the mobile subscriber (MS) using said calling number (MS-ISDN) and said allocated bearer capabilities (BCi), PA1 a) the fixed network including a fixed network switching means (PABX, CPE, O-EX, T-EX) for receiving a call setup request (IAM, SRI) from a call originating subscriber (SS1-SS4; MS1-MS8), said call set-up request having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested; and PA1 b) the mobile communication network comprising: PA1 b1) a mobile radio communication network (PLMN-A) switching means (GMSC, HLR, VMSC/VLR, MSC) for receiving the call set-up request transferred from the fixed network switching means via said network interface; and PA1 b2) a contour storage means (CM) for storing for each subscriber (MS1-MS4) of said mobile radio communication network (PLMN-A) a number of predefined bearer capability contours (BCC1, BCC2, BCCN) indicating services supported by the mobile communication network for handling said different types of calls; and PA1 b3) a contour selection means (CSM) for comparing a content of said second portion of said received call set-up request (SRI) with said predefined bearer capability contours and for selecting a predefined bearer capability contour which provides a best match to said content of said second portion; and PA1 b4) an assembly means (AM) for composing a final mobile bearer capability (BC.sub.F) from said contents of said received second portion (BC2) and said best match selected predefined bearer capability contour; and PA1 b5) a setting-up means (HLR, VMSC/VLR , MSC) for allocating bearer capabilities (BC) in the mobile radio communication network (PLMN-B) in accordance with said final mobile bearer capability (BC.sub.F) and for setting-up said requested call to the mobile subscriber (MS) using said calling number (MS-ISDN) and said allocated bearer capabilities (Bci). PA1 a) the fixed network including a fixed network switching means (PABX, CPE, O-EX, T-EX) for receiving a call set-up request (IAM, SRI) from a call originating subscriber (SS1-SS4; MS1-MS8), said call set-up request having a first portion including a calling number (MS-ISDN) of a called mobile subscriber (MS) and a second portion including information about the type of call requested; and PA1 b) the mobile communication network comprising: PA1 b1) a mobile radio communication network (PLMN-A) switching means (GMSC, HLR, VMSC/VLR, MSC) for receiving the call set-up request transferred from the fixed network switching means via said network interface; and PA1 b2) a contour storage means (CM) for storing for each subscriber (MS1-MS4) of said mobile radio communication network (PLMN-A) a number of predefined bearer capability contours (BCC1, BCC2, BCCN) indicating services supported by the mobile communication network for handling said different types of calls; and PA1 b3) a contour selection means (CSM) for comparing a content of said second portion of said received call set-up request (SRI) with said predefined bearer capability contours and for selecting a predefined bearer capability contour which provides a best match to said content of said second portion; and PA1 b4) an assembly means (AM) for composing a final mobile bearer capability (BC.sub.F) from said contents of said received second portion (BC2) and said best match selected predefined bearer capability contour; and PA1 b5) a setting-up means (HLR, VMSC/VLR, MSC) for allocating bearer capabilities (BC) in the mobile radio communication network (PLMN-B) in accordance with said final mobile bearer capability (BC.sub.F) and for setting-up said requested call to the mobile subscriber (MS) using said calling number (MS-ISDN) and said allocated bearer capabilities (Bci),
ISDN: IAM (MS-ISDN.sub.k, optional BC.sub.k, optional LLC, optional HLC);
As explained above, the PSTN can only transfer the MS-ISDN and no compatibility information whatsoever. Thus, the GMSC either receives no bearer capability information at all or incomplete bearer capability information filtered by the network protocols, even if optionally defined as BC.sub.k in the ISDN-case (reference 2!). The home location register HLR contains entries individually associated with each subscriber of the network PLMN. For each mobile subscriber 1, 2 etc., there is stored a plurality of MS-ISDN/bearer capability BC.sub.1, BC.sub.2, . . . , BCN pairs. A basic MS-ISDN relates to "speech" bearer capability, for example when the set-up request is made from a PSTN. There are additional pairs of MS-ISDN/BC identifications for "data", "fax G2/3" etc. As can be seen from FIG. 3b, according to the specified incoming number MS-ISDN (MS-ISDN, MS-ISDN.sub.1, MS-ISDN.sub.2, MS-ISDN.sub.N), the home location register HLR can provide in response to the send routing information SRI command a provide roaming number message PRN to a visitor location register VMSC/VLR, in which the required bearer capability is derived from the respective pair indicated for the specific called subscriber of PLMN-A.
Thus, the listing of multiple MS-ISDN numbers in the home location register provides the appropriate bearer capabilities, even if no (PSTN case) or insufficient (filtered by the network protocols in the ISDN-case) compatibility information is received. This is indicated with case A in FIG. 3c. Only in the unusual case B and only for the ISDN/PLMN case where the compatibility information is not filtered, the bearer capability can be deduced/translated from the received compatibility information/optional HLC, as is indicated in FIG. 3c.
This procedure is called "multiple-numbering scheme", since in both cases A, B the home location register HLR will have to store for each subscriber of PLMN-A the plurality of MS-ISDN/BC association pairs.
Thus, if the fixed subscriber (or the mobile station MS* in PLMN-A or PLMN-B) wants to initiate a call set-up for a facsimile call, it will dial (transmit) a different MS-ISDN number (which it knows beforehand and which is beforehand stored in the home location register HLR), in order to make sure that the PLMN provides the correct bearer capabilities dedicated to supporting such a facsimile basic service. That is, each MS-ISDN is always defined and related to a specific bearer service or teleservice, when interworking with the PSTN.
Thus, when interworking with the ISDN, the multiple-numbering scheme is also used, if insufficient bearer capability information (i.e. compatibility information) is received by the HLR. Following the GSM/DCS standards, subscriber stations assign multiple MS-ISDNs to bearer service and/or teleservice to provide different types of mobile terminating calls, i.e. different types of calls. The bearer services and teleservices might be of extensive and various types, as defined by the PLMN standards. The mobile subscribers thus need to request from the mobile operator several subscriptions for each of their data service applications supporting different data rates. Since there are different combinatorial characteristics defining these bearer services and teleservices (e.g. facsimile calls, unrestricted digital data calls, 3.1 KHz data calls of synchronous, asynchronous, packet, non-packet, PAD, transparent or non-transparent type and also of the different access user rate of 300 bps, 1200 bps, 75/1200 bps, 2400 bps, 4800 bps, 9600 bps; bps=bit/s) the home location register HLR must be very large and the mobile subscriber must apply for a large variety of subscriptions from the PLMN-operator (reference 6!: European Digital Cellular Telecommunications System (Phase 2); General on Terminal Adaptation Functions (TAF) for Mobile Stations (MS) (GSM 07.01); ETSI, European Telecommunications Standards Institute; September 1995).
Apart from this, there is another major disadvantage, that the setting-up of the calls may even fail when using the multiple-numbering scheme, as will be briefly explained below.
Assume a case, where the subscriber station SS1 (connected to an ISDN-network) wishes to originate the said facsimile transmission to the mobile station. Assume further, that by accident not the appropriate MS-ISDN.sub.2 (see FIG. 3b), but the incorrect MS-ISDN.sub.1 is included in the IAM and SRI message transferred to the home location register HLR. The HLR will thus provide bearer capability BC1 in the PRN message to the visitor location register. This means, that the visiting location register in the second stage of call set-up sets up a call with bearer capabilities BC.sub.1 dedicated to "data". The result is obvious: the call fails, since "facsimile data" are transferred up to the PLMN, while the PLMN provides a bearer capability adapted for "data".
Thus, the disadvantages of the multiple-numbering scheme when using a PSTN/PLMN or a ISDN/PLMN interconnection can be summarized as follows: